Oh hey, that thing happened that one could easily see was going to happen [0]. The writing was on the wall for XSL as soon as the browsers tore out FTP support: their desire to minimize attack surface trumps any tendency to leave well enough alone.
I wonder what the next step of removing less-popular features will be. Probably the SMIL attributes in favor of CSS for SVG animations, they've been grumbling about those for a while. Or maybe they'll ultimately decide that they don't like native MathML support after all. Really, any functionality that doesn't fit in the mold of "a CSS attribute" or "a JS method" is at risk, including most things XML-related.
I wonder what the next step of removing less-popular features will be. Probably the SMIL attributes in favor of CSS for SVG animations, they've been grumbling about those for a while. Or maybe they'll ultimately decide that they don't like native MathML support after all. Really, any functionality that doesn't fit in the mold of "a CSS attribute" or "a JS method" is at risk, including most things XML-related.
[0] https://news.ycombinator.com/item?id=43880391